This invention refers to an electromagnetic relay of the type of relays that essentially incorporate a coil, a core, an armature, fixed and movable contact strips with associated terminals, as well as components for indicating the operational mode of the relay.
The relay, object of the present invention, tries to satisfy the demands of present technology in the applications of these components, mainly in these related to the automation of industrial process systems which involve, without harm to observe, visually, the state of the xe2x80x9cOperative Relayxe2x80x9d. Furthermore it must meet the recommendations published in the low Voltage Directive relating to the application of these components.
The programmed control systems require that the parts used as xe2x80x9cinterfacexe2x80x9din the signal inputs or outputs, (electromagnetic relays or solid state relays), be protected against instant over voltages carried in the lines or generated by the relay on disconnecting the coil.
To achieve this protection circuits suppressers with diodes, varistors, condensers, etc, are used that are connected in parallel or in series with the relay coil. These circuits can be located in the exterior of the relay for which it is necessary to have a base plate specially designed for this purpose, depending on single manufacturer, or better inside the relay. This last solution is that preferred by the design and maintenance technical personnel because it allows the using of standard base plats available in the market or including those already installed in the control equipment facilitating the maintenance work.
The positioning of those circuits in the interior of the relay presents problems due to the reduced dimensions of the available spaces likewise the difficulty of keeping the necessary isolation between these circuits and the output contact block of the relay. These problems are greater when it is a relay of small size that must meet with the international rules relating to the isolation between coil and contacts and with the protection levels established in said rules.
Electromagnetic relays conventionally incorporate a coil mounted on a support from which extends a magnetic plate, likewise it has a rocker arm on which are mounted movable contact strips that move by tilting the arm towards the fixed contact strips due to the excitation of the coil.
The mechanics of these relays differs little between the different models available on the market. Essentially they consist of a magnetic circuit in the form of a U on one of whose arms a coil is a inserted and on the other a magnetic piece is held which on tilting closes the magnetic circuit. The force of attraction resulting on connecting the coil is applied by means of an isolating striker against the group of movable contact bearer strips. The supply terminals for the coil and those corresponding to the contact bearer strips extend to the exterior of the casing in a way that they maybe plugged into a base plate or appropriate female terminals.
In these relays the incorporation of protection circuits is found in every case to be limited to very simple circuits, made up of few components, which have to be distributed throughout the gaps allowed by the mechanics of the relay, without hindering the movement of the moveable parts y maintaining the necessary isolation. Connections between cables are normally done by means of soldered cables, such that the mentioned isolation distances are seriously affected and the labour employed is expensive.
The possibility of integrating the circuitry in the same relay established on an interchangeable board, likewise the integration of the different parts that make up the relay in a series of easily mounted base modules makes feasible the development of an electromagnetic relay such as that described below.
The electromagnetic relay proposed by this invention meets, to complete satisfaction, the expectations set out, being essentially structured by a multi-modular set of easy mounting that fundamentally has, a casing that has a receptacle designed to incorporate a small interchangeable circuit board, an armature on which are mounted the strips, terminals and magnetic plate, a spool for mounting the coil and a base module.
On the base module the support and spool of the coil with its different parts is mounted, all being enclosed in the interior of a large cavity defined by the casing.
The casing shows an open rectangular prismatic configuration for its lower face which leads to the forementioned internal cavity, which is found internally limited in height by a horizontal separation partition that constitutes the base of the little rectangle established in the upper face of the casing.
The circuit therefore will stay stored in the fore mentioned receptacle covered by an easily removable cover, which is extracted in order to proceed to change the small circuit board in this way making possible the easy interchangability of circuits with the object of guaranteeing different applications for the relay.
As well, the base module will be made up of a base plate from which extend some lateral partitions, which have openings for incorporating means of fastening the support and spool of the coil.
Likewise said base plate has a series of openings through which the relay terminals protrude to the exterior.
The mentioned armature is conceived as a support piece that integrates a series of vertical cavities for the incorporation of a movable strip and each fixed strip, likewise a lever that indicates the condition of the relay.
Likewise the internal structure has an opening that extends at high level in vertical position and that is made for the introduction of one of the arms of the magnetic circuit.
The spool of the coil is made up of a cylindrical part finished off in a lower base laminate that extends with respect to said part which has some end notches established for connection of terminals.
Likewise the said cylindrical part has an upper base sheet that extends in a promontory with a series of notches arranged in the same way vertically as the lower base, these upper notches being conceived to facilitate the joining of the fore mentioned terminals previously connected to the lower notches.
Starting from this structure of the constituent parts of the relay, a special configuration of the internal movement mechanism of the relay is conceived, that conventionally incorporates the fore mentioned indicating lever, and means of observing the relay condition, consisting of a visor situated in the upper part by which is observed if a signalling plate is below the visor in which case the relay is found to be activated.
The mechanism incorporates to such effect the armature that has a broad upper base situated over the core of the coil, from which extends a lower inclined arm that is positioned by its upper part against a strap that constitutes an elastic element against which it tilts, finding the lower extreme of the arm arranged in contact on a striker that acts moving the indicating lever.
The striker incorporates a broad vertical frontal face upon which contacts the fore mentioned arm of the rocker, from which subsequently extends at half level a rectangular ring that has in its middle part each with opposite ledges that are linked to the movable strip steadying its movement, having the mentioned rectangular ring in its extreme opposite to the frontal face with a latch in the form of a xe2x80x9cTxe2x80x9d that links to the indicating lever.
The mechanism thus conceived is found in its rest position with the movable strip in contact with one of the fixed strips.
When the coil is excited or when the push button is manually depressed, the rocker arm tilts and at the same time causes with the extreme lower part of its arm the movement of the striker, producing at the same time the movement of the movable strip towards the other fixed strip, likewise, the movement of the indicating lever, that will show its limits through a window made in the upper cover of the casing.